Not correctly reading serial port data after first cycle

I set up a VI for serial communication using RS232 with a pressure transducer meter. The pressure readings are in a loop along with a series of calculations in that loop. The readout from the first cycle is correct, but i just see garbage characters on every subsequent cycle. The VI was running fine when the loop was just reading the pressure data and not performing any calculations. What could be the reason for this discrepancy.
The OS is windows NT and software is Labview 6.1
Thanks

Thanks for your response,
I am using a VISA. The bytes at serial port are fixed, that is for a particular command the response number of bytes is fixed. The read operation in the first cycle (of a loop) is correct but it reads garbage characters for every other cycle. I am using a 9600 baud rate and the meter responds directly in strings, no handshake is used.
Thanks for the response,
PS: The computer with the code is not connected to the net, i will need to transfer it to post the code.

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Attachments:
MKSRead.vi ‏55 KB

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Attachments:
MKSRead_mod.vi ‏68 KB

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Attachments:
NI Spy - before freeze.JPG ‏104 KB
NI Spy - after freeze.JPG ‏108 KB

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Hi,
I have sent 5 bytes(for example: "0","2","F","1","/n") to serial port and used VISA Read. But I only can read 0. The right result is in the second line of the read string window, The first line is void. Generally speaking, "02F1" should in the first line,then I can read them correctly. The following picture is the result.
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帖子被hengfo在09-17-2007 03:57 AM时编辑过了
Attachments:
read string.JPG ‏6 KB

Hello,
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Morning,
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BTDevice.java
public boolean connect(String addr)
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String s="";
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Parse String.png ‏16 KB

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Good news!
I beleive I have found the cause and solution. At least now I am able to reproduce the problem at will and therefore, hopefully prevent it.
I discovered that there is nothing wrong with my AJA KONA setup, as I was able to capture with both QuickTime movie capture and Adobe Premier just fine. But every time I try capturing in FCP I get unreadable capture files (since 2 days ago).
Trying all possible capture settings, capture presets or easy setups did nothing. (although capturing thru Firewire still works every time).
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